1. Field of the Invention
The present invention relates to a pulse data detecting apparatus mounted on a human body to measure pulse data, pulse data detecting method, and the like.
2. Description of the Related Art
Conventionally, various types have been available for apparatuses of measuring pulse of a human body. By way of example, a method of obtaining an electrical signal flowing at both ends of the trunk across the heart (an application of an electrocardiogram) and a method of measuring the sound of heartbeat together with measuring a blood pressure are known. Also, based on using the fact that the light absorption amount changes with change in concentration (density) of hemoglobin flowing through capillary vessels distributed over the body surface, a (so-called optical) method of using the principle that the light amount of reflected light changes with heartbeat is also known as another example of the method for measuring pulses. In this method, the human skin is irradiated with light such as visible light (green or red) or near-infrared light and a change in body-surface reflected light or a change in absorption light amount of hemoglobin by body transmission light is measured.
Among these various types of measuring devices, a scheme called an optical type has been disclosed in, for example, Japanese Patent Application Laid-Oben (Kokai) Publication No, 2007-105338 and Japanese Patent Application Laid-Open (Kokai) Publication No. 2009-231577, describing a technology of measuring pulse data based on a detection signal obtained by receiving, at a light-receiving element, reflected light of light applied from a light-emitting element to the body surface.
FIG. 16 is a perspective view of an example of external appearance, schematically depicting the structure of a pulse data detecting apparatus 100 described in Japanese Patent Application Laid-Open (Kokai) Publication No. 2009-231577. In FIG. 16, on a circuit board 101 having various circuits mounted thereon, a light-emitting element 102 and a light-receiving element 103 are arranged with a predetermined space apart from each other. Around the light-emitting element 102 and the light-receiving element 103, a light-shielding block 104 is arranged. The light-shielding block 104 is formed higher than the light-emitting element 102 and the light-receiving element 103.
FIG. 17 is a cross-sectional view of the state of the pulse data detecting apparatus 100 depicted in FIG. 16 at the time of pulse data detection. The pulse data detecting apparatus 100 is pressed onto the skin surface of the arm or the like of a test subject so as to face the light-emitting element 102 and the light-receiving element 103 and the skin surface each other, and is fixed as required. Here, the light-shielding block 104 makes close contact with a skin surface 200. As a result, light applied from the light-emitting element 102 is prevented from being directly received by the light-receiving element 103, and reflected light from the inside of the skin reaches the light-receiving element 103. The pulse data detecting apparatus 100 measures a blood flow rate from an absorption amount of light with a certain wavelength that changes with the blood flow rate of a capillary vessel 201 inside the body, and detects pulses from that change.
Meanwhile, the pulse data detecting apparatus 100 disclosed in the above-described patent documents, etc., is influenced by the condition of the body surface to be measured, for example, uncertainties such as unevenness in distribution of lentigines (moles), body hair, body color, capillary vessels on the skin surface and in changes of blood pressure. As a result, extremely large unevenness may occur in the measurement result. In particular, in an environment with adverse conditions, ratios of disturbance noises such as ambient light, device vibrations, and a shift of a measurement region and disturbance noises such as changes of blood flows due to body movement originally included in blood flow components are increased, and thereby pulses cannot be accurately detected.